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COMPARISON OF SHIP-MODEL TESTS IN SLOTTED-WALL CHANNEL AND IN A TOWING TANK

Previous small-scale experiments on ship models held in a water channel with slotted walls were extended by fitting a drag balance. Models with blockage ratios of about 1 1/2 and 5 percent were used with several slot widths. Even with the larger model, satisfactory observations of resistance and wave profiles were made which differed only slightly from those obtained when the models and balance were transferred to a large towing tank. Part of the discrepancy was evidently caused by the stationary waves that appear spontaneously at stream Froude numbers exceding about 0.45 in a channel preceded by a contraction. The addition of a small ridge across the bed of the contraction almost annulled these waves over a small range of stream velocity, and then the observations in the channel and in the tank were nearly identical.